[unreadable] There has been a dramatic increase in noninvasive microimaging of small animal tumor models at the University of Wisconsin over the past two years. This interest was mainly stimulated by the purchase of a MicroCAT I (ImTek) microCT scanner capable of 40-micron spatial resolution in live mice. The utility of our microCT scanner is enhanced significantly by the availability of cell-selective CT contrast agents being developed by Dr. Jamey Weichert of the Contrast Agent Development Lab, a joint effort between the Department of Radiology and the University of Wisconsin Comprehensive Cancer Center (UWCCC). To our knowledge, these agents are the only molecular CT contrast agents that are suitable for use with microCT scanners. Accordingly, our laboratory has reported the detection of numerous soft tissue tumors including breast, pancreatic, lung, intestinal, prostate, as well as sub 300-micron liver tumors in live mice. We are now able to "fly through" the lumen of blood vessels less than 150 microns in diameter using our long-acting vascular contrast agent and can also perform virtual colonoscopy in live mice. Collaborative microimaging efforts within the University exploded with the awarding of a P20 Molecular Imaging Center Planning grant, which formalized interactions between imaging scientists and Mouse Models of Human Cancer consortium investigators directed by Dr. William Dove, as well as other cancer biologists. MicroCT demand has overwhelmed our capacity. In addition to creating tremendous campus demand, our advanced microCT molecular imaging efforts have resulted in collaborative requests from extramural academic investigators as well as pharmaceutical companies, and even ImTek. The aim of this proposal is to acquire an ImTek MicroCAT-II microCT scanner. This instrument affords our researchers sub-18 micron spatial resolution, the capability of scanning live rats by virtue of its larger gantry and detector, faster acquisition and reconstruction times, and microPET-compatible beds. A second scanner will permit us to continue development of our innovative cell-selective contrast agents, while continuing to advance novel small animal tumor imaging strategies. As the leader in cell-selective CT contrast agent development, it is our intent to continue development of these unique agents and make them available to other microCT investigators. [unreadable] [unreadable]